Ford 3.5L TiVCT spark knock

[ford_tech]

Hello
Alot of customers come to my shop with broken pistons due to low octane fuel causing spark knock on normal or higher operating temperature and higher gear with light throttle.
I?m confused with ford tuning since it is not detailed as GM tuning. So im looking for a spark retatd within these conditions but failed to get a good results.
I hope someone has an idea.

[ford_tech]

Anyone

[Thatwhite5.0]

I posted this in another thread. This is 2 posts combined.


The tables fluctuate. Since ford has VCT, they knew they couldn't use just one spark table because with alternating cam timing, adjustments of the spark would need to happen too, so they used 2 spark tables, borderline and mbt spark tables. Borderline is normally the lowest timing value with mbt being max. Mbt is like a spark limit for loads 40% +. Timing advance usually will not go above mbt in most conditions. Timing will run off borderline with mbt as the max. Timing will run in between borderline and mbt.


Spark advance limit : 4
Borderline : 17
Mbt : 26.
Timing should end up at 17 + 4 = 21 degrees.

Spark advance limit : 4.
Borderline : 17
Mbt : 19
Timing will stop at 19 degrees. Until you raise mbt to 21 degrees or more, you will not hit the targeted timing


The only time borderline will be higher than mbt is at low loads, between 0% load to around 35% load, borderline will be higher, more advanced than mbt Borderline will drop below mbt somewhere around 35% or 40% load, mbt advances more than borderline.

Depending on what year you're working on, some of your mapped points will have mbt that is always higher than borderline. That has to do with when the mapped points come into effect. If they do not come into play in any low load situation, mbt will stay higher than borderline.

(Sent from my phone)


I wouldn't add the timing on MP 0 - 12. At those loads, your IMRC should be open and you're in 14+ mapped points. There are different ways you can add timing so you try what you feels best. Realistcally, you can add timing to roughly 8 total cells in few mapped points and have your targeted timing.

Have your targeted timing value you're wanting to test in mind. Don't just start adding.

Check your total spark limiters, make sure they're high enough for the timing you want.
Check your spark advance limit and see what it's set to. Yours is at 10. I'd first go do a datalog and see what the timing is doing currently. If the car is adding or retarding timing any where, adjust it. If you see the knock sensors are adding 6, 7, 8 degrees in certain cells/ mapped points. Add some timing into the cell. if it's adding 6 degrees, add 2 degrees to the cell to make the knock sensors only add 4 degrees. Or add 3 to make the knock sensors add 3 degrees. Add timing in 0 - 12 where it's needed. Once you get your tables so they're not adding an insane amount of timing. Change your spark advance limit to 4 in WOT areas. The lower loads I'll let add a couple of more degrees.
If you're getting knock retard (example) at 2000 RPM .40 load. Compare the cell in borderline and MBT for that mapped point. If you see that MBT is lower than borderline, instead of removing timing in borderline, you can add a degree or two in MBT, run it again and check if that got rid of your retard. If that did not get rid of knock, then pull the timing from borderline.

WOT Borderline
Lets say our target is 23 degrees. I change 3000 - 8000 RPM, the last two rows, which for mine are .9 and 1.1 load. Be careful not to add to much timing at low RPM's because they do retard back to single digits. I'll change 1.1, to 18 degrees, 18 + 4 = 22. Then I'll change .9 load to 19 degrees which will give me my 23 degree target.

MBT
When I look for good WOT timing, I'll set my MBT to a number that's high for my tests. I'll have 29 in 1.1 load and 30 in .9 load. My spark advance limit won't allow more than 4 degrees to be added. Targeting 23 degrees, MBT will not be in the way of my tests and I can test up to 29 degrees with that MBT. Once you find your timing, you can copy your WOT borderline to the same MBT cells and add 4 or 5 degrees.




On gen 2s, I'd apply this to all the mapped points used during WOT. Also when you raise .9 timing, check the cells in the lower loads to make sure they're flowing correctly. You can get knock retard when timing advances, retards and advances. Going from 25 to 16 to 19 degrees.

[murfie]

He's asking about a 3.5L. Possibly a direct injection, turbo charged engine. If that's so, it's more likely he is describing low speed pre-ignition. LSPI, is uncontrolled by nature. If you didn't commanded the timing the ignition is happening at, you can't retard it to avoid the detonation. Only thing that can be done for protection is run an approved oil, higher octane fuel, and block the conditions it is most know to happen in using the LSPI tables.

[ford_tech]

Thanks for your inputs, the engine is not turbocharged and not gdi. Im getting detonation on this conditions:
Normal operating temperature
Higher gears
Low rpm below 2000 usually.
I was confused when to retard the timing, Vcm suite doesnt collect that conditions together so that i retard the engine in these conditions.